The present invention relates to structural systems. More particularly, the present invention relates to modular systems for the construction of frameworks.
Certain permanent and semi-permanent free-standing frame members require systems that can be readily assembled and disassembled. The frame members are required to provide a durable and stable structure, be easy to handle and be installable by a limited number of persons. The frame members can form a wide variety of shelter frames such as outdoor tents, circus tents, playground equipment, geodesic domes, greenhouses, swimming pool structures, etc. The frame members can also form internal structures, such as furniture, stands, shelving, artwork, etc.
One problem with many adjustable framing systems is that they use telescoping members to assemble and disassemble a structure. The telescoping members are costly, complicated and tend to make the structure less rigid or strong. Some systems, for instance, require inner and outer spring loaded tubes and a bolt or clamp that tightens the members together to form a member having a desired length. Other systems require an internal threaded rod or ball screw and an internally threaded member that threads onto the ball screw. When the threaded member is turned, the length of the member shortens or lengthens. Still other systems require a plurality of internal rods having threaded ends connected by a right angle gear and a second mating gear that couples to a handle, which extends outside of the member to enable an operator to turn the handle and thereby turn the rods to lengthen or shorten the member.
Obviously, each of the above adjustable framing systems is more complicated, costly, and heavy than simply using non-adjustable sections of tube and standard, nonadjustable tube fittings, which form a system that is difficult to assemble and disassemble. In order to put together and take apart the above systems, the members need to be adjustable. A need therefore exists for a framing system that allows a structure to be assembled and disassembled without having to telescopically move a tubing member, i.e., shorten or lengthen, the member along its centerline. The system should optimally take advantage of the relatively low cost and structural stability provided by off the shelf tubing.
There are known framing systems for releasably interconnecting frames that do not require telescoping. These systems have typically used screw connectors or quick disconnects, which have a number of drawbacks. First, in some systems the connectors or quick disconnects are formed integrally as part of the frame member. Here, the length of the frame members must be carefully machined, which adds to the expense of manufacture. Second, the integral connectors often require more than one person for assembly. Third, many of the connectors are limited to providing only right-angle connections. Such connectors obviously limit the shape and flexibility of the resulting structures.
A need therefore further exists for a non-telescoping framing system that has non-integral connectors, which do not require precise and expensive machining and tolerances. Further, the system should allow for members to be connected at multiple angles and for curved members.